On March 27, 2018, Prof. Christian Ungermann visited Institute of Biophysics, CAS and gave a lecture entitled “Autophagosome maturation and fusion”. The lecture was hosted by Prof. Hong Zhang, and was part of the special lecture series named “Shizhang Bei Lecture” of Institute of Biophysics.

Prof. Christian Ungermann`s lab is focused on the machinery responsible for membrane dynamics (fission and fusion) at endosomes and lysosomes/yeast vacuoles. Their main interests are small regulators, the Rab GTPases Rab5 (Vps21) and Rab7 (Ypt7), and their interaction partners, in particular the tethering complexes CORVET and HOPS. A second major focus are membrane contact sites of vacuoles, in particular with mitochondria and the ER, which also depend on the Rab7-like Ypt7.
 
In the presentation, Prof. Christian Ungermann introduced that Endosomes and lysosomes are part of a very dynamic membrane system. During endocytosis, cell surface proteins are transported to the lysosome/vacuole, which carry the Rab7-like Ypt7 protein. They pass first through the early endosome, which converts into the late endosome that then fuses with the lysosome. And his lab interested in the mechanism of organelle maturation in the endolysosomal system, taking yeast as a model system.

He then provided their recent insights into the mechanisms on how autophagosomes mature and become fusion competent. The guanine nucleotide exchange factor (GEF, Mon1–Ccz1) has at least two destinations: endosomes and autophagosomes. Mon1–Ccz1 has distinct binding sites for organellar proteins, including Atg8. And regulation of its targeting will likely include additional modification and proteins. Their data provide evidence that the Rab7 GEF complex of Mon1 and Ccz1, which activates Rab7 on endosomes, is diverted to the autophagosome and subsequently required for fusion.

Finally, he discussed the implications in their understanding of organelle maturation. By using a novel in vitro assay, they can measure the autophagosome fusion with vacuoles. And they found that fusion of autophagosomes depends on the autophagosomal SNARE Ykt6.
 
Prof. Christian Ungermann gave the lecture with vivid words, rigorous logic and great passion, which can be a lively lesson for the audience. Many investigators from Institute of Biophysics attended the lecture. After the lecture, Prof. Christian Ungermann and the audience shared their views on the issues of common interest.

Prof. Christian Ungermann was giving the lecture

Prof. ZHANG Hong hosted the lecture

 Scene of the lecture

Report by ZHANG Hong group

Picture by WANG Qiang